Room-temperature vulcanizing (RTV) silicone rubber compositions are in widespread use for numerous applications. The cured elastomers exhibit excellent chemical, dielectric, adhesive and physical properties, including toughness, durability and resistance to environmental effects, making them ideally suited as coating and encapsulation materials for waterproofing and other protection (e.g., against corrosion) of electric motors, power system apparatus, metal hardware and structures, oil- and gas-storage tanks, pipes and transport systems, bridges, abutments, roofs, metal barriers, etc. Unlike many other conventional materials, moreover, which are often difficult to prepare, apply, and/or maintain, RTV silicones do not require complex measuring or mixing procedures (which commonly result in products of short or indeterminate pot life), and they do not chalk, flake, peel, embrittle, or otherwise degrade (at least by most mechanisms) over long periods of time. In addition, the low Durometer values that are typically exhibited by RTV silicone rubbers permit ready mechanical penetration, and thus facilitate the use of tools for effecting the removal of coated panels and the like for purposes of maintenance and repair of protected parts and units.
RTV silicone materials normally cure through water-initiated chemical mechanisms, and therefore react and set up quickly upon exposure to ambient moisture. While this property is very advantageous in most circumstances, it also has the adverse effect of precluding, as a practical matter, the use of certain desirable application techniques. Most notably, efforts to package and dispense RTV silicone coating materials in aerosol form have heretofore been frustrated by the formation of cured deposits, on and around valve components, that clog passages and immobilize parts that have been contacted by the silicone material and that become exposed to the atmosphere (e.g., upon initial discharge or during storage, particularly under high humidity conditions); the shelf-life of such packages was no more than a few months, following initial use.